Abrasive article with uniform height abrasive particles

ABSTRACT

A method of making an abrasive article including the step of preparing a master plate with a surface having a shape. Depositing a spacer layer on the surface of the master plate. A slurry containing an adhesive and abrasive particles is deposited on a surface of the spacer layer. A substrate embedded with abrasive particles having a surface generally complementary to the surface of the master plate is fabricated. A spacer layer is formed by various method controlled the height of the protruded abrasive particles. The master plate and the spacer layer are separated from the substrate to expose abrasive particle protruding a substantially uniform height. An abrasive article made according to this method is also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefits of the filing date of U.S. Provisional Patent Application Ser. No. 61/187,658 filed Jun. 16, 2009, which is entitled “Abrasive Article with Uniform Height Abrasive Particles” which is hereby incorporated herein in its entirety by reference.

FIELD OF THE INVENTION

The present application is directed to an abrasive article with abrasive particles that protruded a substantially uniform height above a reference surface, and a method of making and using the same. The present method permits the manufacture of abrasive articles with micron and nano-scale diamond particles.

BACKGROUND OF THE INVENTION

Read-write heads for disk drives are formed at the wafer level using a variety of deposition and photolithographic techniques. Multiple sliders, up to as many as 40,000, may be formed on one wafer. The wafer is then sliced into slider bars, each having up to 60-70 sliders. The slider bars are lapped to polish the surface that will eventually become the air bearing surface. A carbon overcoat is then applied to the slider bars. Finally, individual sliders are sliced from the bar and mounted on gimbal assemblies for use in disk drives.

Slider bars are currently lapped using a tin plate charged with small diamonds having an average diameter of about 250 nm. The tin lapping plate is prepared in several steps. The first step is to machine a flat tin plate. The second step is to machine grooves or geometrical features that promote lubricant circulation and control of the thickness of the hydrodynamic film between the oil lubricant and the slider bars.

The third step is to charge the tin plate with diamonds, such as illustrated in U.S. Pat. No. 6,953,385 (Singh, Jr.). Singh teaches applying a ceramic impregnator downward on the lapping plate surface with a controlled force while the diamond slurry is supplied. The diamonds are impregnated into the relatively soft tin layer of the lapping plate. Fourth, the impregnated lapping plate is dressed with a dressing bar. The dressing bar reduces the height variation by pressing the larger diamonds further into the tin, producing a more uniform height of the diamonds. Several runs of the dressing bar help improve height uniformity of the abrasive diamonds impregnated into the tin. Current processes are economically wasteful since over 90 percent of the diamonds are lost and unrecoverable in the process.

During use, the lapping plate is flooded with a lubricant (oil or water based). The viscosity of oil based lubricants is about 4 orders of magnitude greater than the viscosity of air. The lubricant causes a hydrodynamic film to be generated between the slider bar and the lapping plate. The hydrodynamic film is critical in establishing a stable interface during the lapping process and to reduce vibrations and chatter. To overcome the hydrodynamic film a relatively large force is exerted onto the slider bar to cause interference with the diamonds necessary to promote polishing. A preload of about 1 kg is not uncommon to engage a single slider bar with the lapping media. Large preloads exacerbate scratches on the slider bars caused by peaks on the lapping plate.

The above described challenges are not unique to disk drive manufacturers, optical component manufacturers and semiconductor manufacturer face similar challenges for fine finishing.

FIG. 1 illustrates a conventional tin lapping plate 50 charged with diamonds 52. Top surface 54 of the tin plate typically has a certain level of waviness. The height 56 of the diamonds 52 tends to follow the contour of the top surface 54, even after the lapping plate 50 is dressed. The waviness of the top surface 54 also creates a non-uniform hydrostatic film 58, creating instability at the interface with the slider bar.

The preload is typically determined by the density of the diamonds and the diamond height variation. As the industry moves to nano-diamonds smaller than 250 nm, the preload will need to be increased to reduce the fluid dynamic film a sufficient amount so the diamonds contact the slider bars. Nano-diamonds are difficult to embed in the tin plate. The risk of free diamonds damaging the slider bar increases. Precisely grooved plates or lubricant reformulation will be required to overcome the fluid dynamic film.

Variables such as lapping media speed, preload on the slider bar load, nominal diamond size, and lubricant type must be balanced to yield a desirable material removal rate and finish. A balance is also required between the hydrodynamic film and the height of the embedded diamonds to achieve an interference level between the slider bar and the diamonds.

FIG. 2 is a schematic side sectional view of a conventional slider bar including a plurality of individual sliders before lapping. Each slider in the slider bar typically includes read-write transducers. As used herein, “read-write transducer” refers to one or more of the return pole, the write pole, the read sensor, magnetic shields, and any other components that are spacing sensitive. Various methods and systems for finish lapping read-write transducers are disclosed in U.S. Pat. No. 5,386,666 (Cole); U.S. Pat. No. 5,632,669 (Azarian et al.); U.S. Pat. No. 5,885,131 (Azarian et al.); U.S. Pat. No. 6,568,992 (Angelo et al.); and U.S. Pat. No. 6,857,937 Bajorek), which are hereby incorporated by reference.

Slider bars with trailing edges composed of metallic layers and ceramic layers present very severe challenges during lapping. Composite structures of hard and soft layers present differential lapping rates when lapped using conventional abrasive lapping plates. The variable polishing rates of the metallic and ceramic materials lead to severe recessions, sensor damage, and other problems.

FIG. 3 illustrates the bar of FIG. 2 after lapping with a diamond-charged lapping plate. The diamond-charged plates cause large transducer protrusion and recession variations, contact detection area variation, substrate recession, microscopic substrate fractures leading to particle release during operation of the disk drive, scratches from free diamonds, and transducer damage.

U.S. Pat. Nos. 7,198,533 and 6,123,612 disclose an abrasive article including a plurality of abrasive particles securely affixed to a substrate with a corrosion resistant matrix material. The matrix material includes a sintered corrosion resistant powder and a brazing alloy. The brazing alloy includes an element which reacts with and forms a chemical bond with the abrasive particles, thereby securely holding the abrasive particles in place. A method of forming the abrasive article includes arranging the abrasive particles in the matrix material, and applying sufficient heat and pressure to the mixture of abrasive particles and matrix material to cause the corrosion resistant powder to sinter, the brazing alloy to flow around, react with, and form chemical bonds with the abrasive particles, and allow the brazing alloy to flow through the interstices of the sintered corrosion resistant powder and form an inter-metallic compound therewith.

U.S. Pat. Publication No. 2009/0038234 (Yin) discloses a method for making a conditioning pad using a plastic substrate 11 having a plurality of recesses 12. The abrasive grains 4 are secured in the recesses 12 by adhesive 31. The second substrate 6 is formed around the exposed portions of the abrasive grains 4. After the second substrate 6 hardens, the first substrate 11 is removed, exposing the cutting surfaces of the abrasive grains 4.

Example 1 of Yin teaches recesses 12 are about 225 micrometers deep and about 450 micrometers wide, with a maximum height difference between the highest and lowest peak of about 25 micrometers. Example 3 of Yin discloses a maximum height difference between the highest and lowest peak of about 15 micrometers. Yin discloses diamond abrasive grains with particle diameters ranging from 10 mesh to 140 mesh. Applicants believe these mesh sizes correspond generally to diamond particles with a major diameter of about 2 millimeters to about 0.1 millimeters. The large size of the diamonds of Yin allow for insertion into the recesses 12. Forming the first substrate 11 with sub-micron sized recesses 12 and then inserting sub-micron size abrasive grains, however, is not currently commercially viable. Sorting sub-micron sized abrasive grains is also problematic.

Other method for orienting and positioning discrete abrasive particles are disclosed in U.S. Pat. No. 6,669,745 (Prichard et al.) and U.S. Pat. No. 6,769,975 (Sagawa), and U.S. Pat. Publication No. 2008/0053000 (Palmgren), which are hereby incorporated by reference.

BRIEF SUMMARY OF THE INVENTION

The present application is directed to an abrasive article with abrasive particles that protruded a substantially uniform height above a reference surface. The present method permits the height the abrasive particles extend above the substrate to be precisely controlled, thereby allowing the hydrodynamic film of the lubricant to also be controlled. The present method is also suited for use with nano-scale abrasive particles.

The present uniform height fixed abrasive article provides a substantially uniform height of the diamonds (dh) with respect to a reference surface. A substantially uniform lubricating hydrodynamic film (hf) forms with respect to the reference surface. The lapping interference (I=dh−hf) defined as the difference between the diamond height and the hydrodynamic film is positive to promote material removal. The cutting forces and hydrodynamic pressure do not excessively deform the substrate as to interfere with the lapping process.

One embodiment is directed to a method of making an abrasive article including the step of preparing a master plate with a surface having a shape. A spacer layer is deposited on the surface of the master plate. A slurry containing an adhesive and abrasive particles is deposited on a surface of the spacer layer. The abrasive particles have a primary diameter greater than a thickness of the spacer layer. A substrate having a surface generally complementary to the surface of the master plate is pressed against the slurry with sufficient force to embed the abrasive particles into the substrate and to penetrate the spacer to the surface of the master plate. The adhesive is at least partially cured to form a reference surface between the abrasive particles with a shape generally complementary to the surface of the spacer layer. The master plate and the spacer layer are separated from the substrate to expose abrasive particle protruding a substantially uniform height above the reference surface formed by the cured adhesive.

The master plate and the substrate can be flat, concave, convex, curvilinear, spherical, or grooved. In one embodiment, features are machined into the surface of the master plate. In another embodiment grooves are machined in the surface of the master plate and complementary grooves are machined in the surface of the substrate. The grooves include peaks and valleys. The peaks in the surface of the substrate include a peak height greater than a peak height of peaks on the surface of the master plate. The abrasive particles are embedded primarily in the peaks of the substrate.

The spacer layer can be deposited by spraying, coating, or printing. In one embodiment, a discrete spacer layer is positioned on the surface of the master plate. By varying the thickness of the spacer layer, it is possible to vary the height the abrasive particles protrude above the reference surface. In one embodiment the spacer layer is a low surface tension material. In another embodiment the thickness of the spacer layer is greater than the height the abrasive particles protrude above the reference surface in order to compensate for deformation during the impregnating step.

Any size or composition of abrasive particles can be used with the method of the present invention. In one embodiment, the abrasive particles are diamonds with a primary diameter of less than about 10 micrometers. In another embodiment, the diamonds have a primary diameter of less than about 1 micrometer.

A hard coat layer is optionally applied to the surface of the master plate before depositing the spacer layer. The cured adhesive occupies gaps between the surface of the substrate and the surface of the spacer layer.

The substrate is selected from one of metals, polymeric materials, ceramics, and composites thereof. The substrate can be a flexible or a rigid material.

The present invention is also directed to a method of lapping a surface of a work piece. An abrasive article according to the present invention is positioned opposite the surface of the work piece. A lubricant is applied to the abrasive article. The surface of the work piece is engaged with the abrasive particles and moved relative to the abrasive article to form a substantially uniform hydrostatic film of lubricant between the surface of the work piece and the reference surface on the abrasive article. The work piece can be machined metal parts, silicon wafers, slider bars for hard disk drives, and the like.

The present invention is also directed to an abrasive article including a plurality of nano-scale abrasive particles embedded in a substrate and protruding a substantially uniform height above a reference surface formed by a cured adhesive located between the abrasive particles.

The present invention is directed to a method of making an abrasive article including the step of preparing a master plat with a substantially flat surface. A slurry containing abrasive particles carried in a fluid. The slurry is dispersed on the master plate to provide a uniformly dispersed particle density onto the master plate. The fluid carrier is evaporated to leave abrasive particles dispersed with a uniform density. A seed layer is deposited on the master plate with distributed diamonds. The seed layer can be sputtered or evaporated onto the master plate containing the abrasive particles. The seed layer can be Chrome or Nickel to promote the electroplating of an additional substrate layer formed from Cupper or Tin or Nickel. The seed layer can be few nanometers thick to provide a conductive path for the electro-deposition of the substrate layer. The substrate layer is deposited from an electro platting process for example. Cupper, Nickel and Tin materials can be grown to many microns thick with very low film stress. Various deposition processes are commercially available such as dry such as sputtering or a wet deposition processes such as plating can be utilized to form the substrate and the seed layer. A combination of processes can also be utilized. First a sputtering process is used to encapsulate the abrasive particles followed by a wet deposition process. Once the thickness of the substrate reaches a desired value of microns, the substrate containing the abrasives is removed from the master plate. Further etching on the surface containing the abrasive particles removes a substantially uniform thickness of the substrate layer revealing the particle abrasives with a uniform height. The height of the particle abrasives matches the amount of material etched from the substrate surface.

The present invention is directed to a method of making an abrasive article including the step of preparing a master plat with a substantially flat surface. A slurry containing abrasive particles carried in a fluid. The slurry is dispersed on the master plate to provide a uniformly dispersed particle density onto the master plate. The thickness of the fluid carrier is controlled to match the desired abrasive protrusion. The fluid carrier is cross linked by thermal or irradiative process to form an immobile polymer structure layer to accept a seed layer. A seed layer is deposited on the polymer structure. The seed layer can be sputtered or evaporated onto the polymer structure containing the abrasive particles. The seed layer can be Chrome or Nickel to promote the electroplating of an additional substrate layer formed from Cupper or Tin or Nickel. The seed layer can be few nanometers thick to provide a conductive path for the electro-deposition of the substrate layer. The substrate layer is deposited from an electro platting process for example. Cupper, Nickel and Tin materials can be grown to many microns thick with very low film stress. Various deposition processes are commercially available such as dry such as sputtering or a wet deposition processes such as plating can be utilized to form the substrate and the seed layer. A combination of processes can also be utilized. First a sputtering process is used to encapsulate the abrasive particles followed by a wet deposition process. Once the thickness of the substrate reaches a desired value, 20 microns for example, the substrate containing the polymer spacer and the abrasives is removed from the master plate. Further etching on the surface containing the abrasive particles removes the soft polymer layer revealing the particle abrasives with a uniform height. The height of the particle abrasives matches the thickness of the polymeric spacer.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a schematic sectional view of a prior art diamond-charged lapping plate.

FIG. 2 is a schematic side sectional view of a conventional slider bar before lapping.

FIG. 3 illustrates the bar of FIG. 1 after lapping with a conventional diamond-charged lapping plate.

FIG. 4 is a side sectional view of a prior art abrasive article with macro-scale abrasive particles.

FIG. 5 is a schematic side sectional view of a fixture for making an abrasive article in accordance with an embodiment of the present invention.

FIG. 6 illustrates an abrasive slurry deposited on the fixture of FIG. 5 in accordance with an embodiment of the present invention.

FIG. 7 illustrates a substrate engaged with the abrasive slurry FIG. 6 in accordance with an embodiment of the present invention.

FIG. 8 illustrates the abrasive particles embedded in the substrate and the spacer layer of FIG. 7 in accordance with an embodiment of the present invention.

FIG. 9 is a schematic sectional view of an abrasive article in accordance with an embodiment of the present invention.

FIG. 10 is a schematic side sectional view of an alternate fixture with a structured surface for making an abrasive article in accordance with an embodiment of the present invention.

FIG. 11 illustrates a substrate engaged with the abrasive slurry of FIG. 10 in accordance with an embodiment of the present invention.

FIG. 12 is a schematic sectional view of an abrasive article with a structure surface in accordance with an embodiment of the present invention.

FIG. 13 is a schematic sectional view of an abrasive article with a concave surface in accordance with an embodiment of the present invention.

FIG. 14 is a schematic sectional view of an abrasive article with abrasive particles sintered to a substrate in accordance with an embodiment of the present invention.

FIG. 15A-D is a schematic sectional view of an abrasive article with abrasive particles dispersed on a master plate in accordance with an embodiment of the present invention.

FIG. 16A-C is a schematic sectional view of an abrasive article with abrasive particles dispersed on a master plate in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 5 illustrates fixture 100 for making a substantially uniform height diamond charged abrasive article in accordance with a method of the present invention. Master plate 102 is machined and polished to a substantially flat surface 104.

Roughness of a surface can be measured in a number of different ways, including peak-to-valley roughness, average roughness, and RMS roughness. Peak-to-valley roughness (Rt) is a measure of the difference in height between the highest point and lowest point of a surface. Average roughness (Ra) is a measure of the relative degree of coarse, ragged, pointed, or bristle-like projections on a surface, and is defined as the average of the absolute values of the differences between the peaks and their mean line.

The master plate 102 is preferably silicon, since wafer planarization infrastructure is capable of achieving a very smooth surface with small waviness values in the order of 1 nm and 100 nm, respectively. The fine finish requirements for the surface 104 include short length waviness, long waviness, and surface finish quality. Planarization of silicon is disclosed in U.S. Pat. No. 6,135,856 (Tjaden et al.) and U.S. Pat. No. 6,194,317 (Kaisaki et al.), which are hereby incorporated by reference.

Once the master plate 102 is machined, a hard coat 106 is preferably applied to protect the surface 104. Surface 107 of the hard coat 106 generally tracks the surface 104 of the master plate 102. The desired thickness 108 of the hard coat 106 can be in the range of about 50 nanometers or greater. In one embodiment, the hard coat 106 is diamond-like carbon (“DLC”) with a thickness 108 of about 50 nanometers to about 200 nanometers. DLC hardness is preferably more than about 5 GPa to adequately protect the surface 104. It is highly desirable to generate DLC hardness in the range of 70-100 GPa.

In one embodiment the DLC is applied by chemical vapor deposition. As used herein, the term “chemically vapor deposited” or “CVD” refers to materials deposited by vacuum deposition processes, including, but not limited to, thermally activated deposition from reactive gaseous precursor materials, as well as plasma, microwave, DC, or RF plasma arc jet deposition from gaseous precursor materials. Various methods of applying a hard coat to a substrate are disclosed in U.S. Pat. No. 6,821,189 (Coad et al.); U.S. Pat. No. 6,872,127 (Lin et al.); U.S. Pat. No. 7,367,875 (Slutz et al.); and U.S. Pat. no. 7,189,333 (Henderson), which are hereby incorporated by reference.

The next step is to apply a spacer layer 110. The spacer layer 110 is preferably a low surface energy coating, such as for example Teflon. The spacer layer 110 acts as a spacer to set height 112 abrasive particles 114 protrude above reference surface 116 on the abrasive article 118 (see FIG. 9). Consequently, by varying the thickness 112′ of the spacer layer 110, the height 112 of the abrasive particles 114 can be controlled. In some embodiments, the thickness 112′ may be different than the height 112 of the abrasive particles 114 to compensate for deformation of the spacer layer 110 during impregnation of the substrate (see FIG. 8). As a result, the thickness 112′ of the spacer layer 110 corresponds to the desired height the abrasive particles 114 protrude above the reference surface 116, but there is not necessarily a one-to-one correlation.

In one embodiment the spacer layer 110 is a preformed sheet bonded or adhered to the surface 107 of the hard coat 106. In another embodiment, the spacer layer 110 is sprayed or printed onto the surface 107, such as disclosed in U.S. Pat. No. 7,485,345 (Renn et al.) and U.S. Pat. Publication No. 2008/0008822 (Kowalski et al.), which are hereby incorporated by reference.

As illustrated in FIG. 6, adhesive slurry 120 of adhesive 122 containing abrasive particles 114 is distributed evenly over surface 124 of the spacer layer 110. Using a spacer layer 110 made from a low surface tension material aids in wetting the adhesive 122. Methods of uniformly dispersing nanometer size abrasive grains are disclosed in U.S. Pat. Pub. No. 2007/0107317 (Takahagi et al.), which is hereby incorporated by reference.

Abrasive particles of any composition and size can be used with the method and apparatus of the present invention. The preferred abrasive particles 114 are diamonds with primary diameters less than about 1 micrometer, also referred to as nano-scale.

Substrate 126 illustrated in FIG. 7 is then pressed against the adhesive slurry 120. In the illustrated embodiment, the substrate 126 is a tin plate. Note that surface 128 of the substrate 126 has some waviness, which will be irrelevant in the finished abrasive article 118 according to the present invention. The substrate 126 can be manufactured from a variety of metals, polymeric materials, ceramics, or composites thereof. The substrate 126 can also be flexible, rigid, or semi-rigid.

As illustrated in FIG. 8, the substrate 126 is applied with a sufficient force F to cause the abrasive particles 114 to substantially penetrate the spacer layer 110, without substantial penetration or indentations in the hard coat 106. The abrasive particles 114 are simultaneously embedded in surface 128 of the substrate 126. The adhesive 122 fills gaps 130 between the surface 128 of the substrate 126 and the surface 124 of the spacer layer 110. The adhesive 122 also follows the contour of the surface 124 of the spacer layer 110, as will be discussed below.

The spacer layer 110 permits the abrasive particles 114 to contact the surface 107 of the hard coat 106 and limits the amount of penetration into the substrate 126. Depending on the material selected, the thickness of the spacer layer 110 may be increased to compensate for deformation during the impregnating step of FIG. 8.

The surface 128 of the substrate 126 preferably has a flatness that is less than about the height of the abrasives particles 114, so the abrasive particles 114 are sufficiently embedded in the surface 128. If the abrasive particles 114 are not sufficiently embedded into the substrate 126, the adhesive 122 may be the primary mode of attachment, leading to release during lapping.

FIG. 9 illustrates the abrasive article 118, with the sacrificial spacer layer 110 removed in accordance with an embodiment of the present invention. Using a spacer layer 110 made from a low surface tension material facilitates removal of the master plate 102. The at least partially cured adhesive 122 forms a substantially flat reference surface 116 from which height 112 of the abrasive particles 114 can be measured.

The waviness of the surface 128 on the carrier is not reflected in the uniform height 112 of the abrasive particles 114 or the reference surface 116. The uniform distance 112 between the peaks 115 of the abrasive particles 114 and the reference surface 116 permits formation of a substantially uniform hydrodynamic film relative to the height 112 of the abrasive particles 114. As used herein, “substantially uniformly” and “substantially flat” refers to both an entire surface of a substrate or an abrasive article and to selected portions of the substrate or abrasive article. For example, localized uniformity or flatness may be sufficient for some applications.

Various processes can be used to activate and/or cure the adhesive 122 to bond the diamonds 114 to the substrate 126 and create the reference surface 116, such as for example ultraviolet or infrared RF energy, chemical reactions, heat, and the like. As used herein, “cure” or “activate” refers to any chemical transformation (e.g., reacting or cross-linking), physical transformation (e.g., hardening or setting), and/or mechanical transformation (e.g., drying or evaporating) that allows an adhesive to change or progress from a first physical state (generally liquid or flowable) into a more permanent second physical state or form (generally solid).

The present method provides a number of benefits over prior art diamond charged lapping plates. The present abrasive article 118 provides a uniform height 112 of the diamonds 114 (“dh”) with respect to a substantially flat reference surface 116. There is no need to condition the present abrasive article 118. Knowledge of the lapping conditions, lubricant type, and the lapped bar can be used to calculate the hydrodynamic film thickness (“hf”) relative to the reference surface 116 formed by the cured adhesive 122. Once the hydrodynamic film thickness is known, the interference (“I”) can be calculated from the uniform height 112 of the diamonds 114 from the hydrodynamic film (I=dh−hf). The substantially flat reference surface 116 provides a generally uniform hydrodynamic film, which translates into uniform forces at the slider bar/abrasive article interface. Constant interference (I) of the abrasive diamonds 114 during the lapping process leads to a notable reduction in occurring of scratches, a substantial improvement in pole tip recession critical to the performance of magnetic recording heads, and a substantial improvement in surface roughness.

Note that the substrate 126 has historically been a tin plate because of ease of charging the diamonds 114 and dressing the plate. Since the height 112 of the protruding diamonds 114 is controlled by the thickness of the spacer layer 110, however, other relatively harder materials are also good candidates for this application, such as for example soft steels, copper, aluminum, and the like.

While the application discussed above is lapping slider bars for disk drives, for the present abrasive article 118 has a wide range of other industrial applications, such as for example lapping semiconductor wafers and polishing metals.

FIG. 10 illustrates a fixture 150 for manufacturing an abrasive article 152 with a structured substrate 154 (see FIG. 12) in accordance with an embodiment of the present invention. The desired structures 156 are machined in the master plate 158. The structures 156 can be linear, curvilinear, regular, irregular, continuous, discontinuous, or a variety of other configurations. Various structured substrates and adhesives suitable for use in the present invention are disclosed in U.S. Pat. No. 6,194,317 (Kaisaki et al); U.S. Pat. No. 6,612,917 (Bruxvoort); U.S. Pat. No. 7,160,178 (Gagliardi et al.); U.S. Pat. No. 7,404,756 (Ouderkirk et al.); and U.S. Publication No. 2008/0053000 (Palmgren et al.), which are hereby incorporated by reference.

In the illustrated embodiment, the structures 156 are a series of grooves. The surfaces 160 of the grooves 156 can be machined with a continuous curvilinear shape, a series of discrete curvilinear or flat shapes with transition locations, or a combination thereof. In the illustrated embodiment, the grooves 156 include valleys 160A, peaks 160B, and side surfaces 160C (collectively “160”). The peaks 160B have substantially uniform peak height 168.

In the illustrated embodiment, the master plate 158 is machined with a hard ceramic material such as TiC or TiN. The hard coat is optional and is not shown in the embodiment of FIG. 10. Spacer layer 162 is then deposited on the surface 160 of the grooved master plate 158 with a thickness 164 corresponding* the desired protruding height of abrasive particles 166. An adhesive slurry 170 including adhesive 172 and abrasive particles 166 is distributed evenly over the grooved surface 174 of the spacer layer 162.

As illustrated in FIG. 11, the substrate 154 with features 182 generally corresponding to grooves 156 is then pressed against the adhesive slurry 170 with a sufficient force to cause the abrasive particles 166 to substantially penetrate the spacer layer 162, without substantial penetration into the master plate 158. The abrasive particles 166 also penetrate into the substrate 154, primarily at peaks 184.

The grooves 182 in the substrate 154 are preferably fabricated with a peak height 180 greater than peak height 168 of the grooves 156 machined in the grooved master plate 158. The greater peak height 180 on the substrate 154 permits the abrasive particles 166 located along critical peaks 184 to be firmly embedded in the substrate 154. Any inaccuracy in the machining of the heights 168, 180 of the grooves 156, 182 is preferably located in the non-critical valleys 190 on the abrasive article 152. Note that portion of the abrasive particles 166′ located in the valleys 190 are not embedded in the substrate 154, but are secured to the substrate 154 by the adhesive 172.

The spacer layer 162 controls the depth of penetration of the abrasive particles 166 into the substrate 154. The adhesive 172 fills any gaps 192 between the surface 186 of the substrate 154 and the surface 174 of the spacer layer 162. The flatness requirement of the substrate 154 is less than about the height of the abrasives particles 166 so as to be embedded a sufficient amount in the surface 186 of the substrate 154.

FIG. 12 illustrates the abrasive article 152, with the sacrificial spacer layer 162 removed. The at least partially cured adhesive 172 forms a substantially flat reference surface 194 from which height 196 of the abrasive particles 166 can be measured. The reference surface 194 also provides a substantially uniform hydrodynamic film relative to the height 196 of the abrasive particles 166.

The grooves 198 in the abrasive article 152 are designed to promote lubricant transfer from inner diameter to outer diameter under centrifugal forces to carry the wear by-products and reduce the height of the hydrodynamic film to promote aggressive material removal. Various geometrical features and arrangement of abrasive particles on abrasive articles are disclosed in U.S. Pat. No. 4,821,461 (Holmstrand), U.S. Pat. No. 3,921,342 (Day), and U.S. Pat. No. 3,683,562 (Day), and U.S. Pat. Pub. No. 2004/0072510 (Kinoshita et al), which are hereby incorporated by reference.

The present method of manufacturing uniform height fixed abrasive articles includes preparing a master plate with a shape that is generally a mirror image of the desired uniform height fixed abrasive article. A hard coat is optionally applied protect the surface of the master plate. A spacer layer is deposited on the master plate or hard coat. An adhesive slurry containing an adhesive and abrasive particles is distributed evenly over surface of the spacer layer. A substrate with a surface that is generally a mirror image of the master plate is then pressed against the adhesive slurry to embed the abrasive particles into the substrate. The spacer layer controls the penetration of the abrasive particles into the substrate. The adhesive fills gaps between the surface of the substrate and the surface of the spacer layer. The substrate containing the embedded abrasive particles is separated from the master plate and the sacrificial spacer layer is removed. The at least partially cured adhesive forms a substantially flat reference surface between the protruding abrasive particles.

It will be appreciated that the present method of manufacturing uniform height fixed abrasive articles can be used with a variety of shaped substrates, such as for example concave surfaces, convex surfaces, cylindrical surfaces, spherical surfaces, and the like. The present method is not dependent on the size or composition of the abrasive particles.

FIG. 13 is a side sectional view of a uniform height fixed abrasive article 250 with a convex surface 252 in accordance with an embodiment of the present invention. The convex surface 252 can be circular, curvilinear, and a variety of other regular and irregular curved shapes. As with the embodiments discussed above, adhesive 254 provides a uniform reference surface 256. The abrasive particles 258 extend a substantially uniform amount above the reference surface 256. The reference surface 256 is also smooth so as to promote a substantially uniform hydrodynamic film. A concave and cylindrical surface can be designed the same embodiments discussed above. The curved abrasive articles (concave and convex surfaces) are particularly suited for polishing machined metal parts, such as for example components for engines and transmissions, where a significant reduction in friction will translate into greater fuel efficiency.

FIG. 14 illustrates a uniform height fixed abrasive article 300 that uses the two step adhesion process disclosed in U.S. Pat. Nos. 7,198,553 and 6,123,612, which are hereby incorporated by reference. Elevated heat and pressure are applied to a sintered powder matrix material and a brazing alloy 302 to create a chemical bond between the abrasive particles 304 and surface 314 of the substrate 306. The sacrificial spacer 308 (shown in phantom) is preferably a soft metal to avoid excessive deformation during heating of the matrix 302.

The matrix 302 lacks the ability to fill the spaces 310 between the sintered material 302 and the spacer 308. A low viscosity curable material 314, such as for example a thermo set adhesive, is provided to fill the spaces 310 and to provide the reference surface 312 between the abrasive particles 304. The curable material 314 also acts as a corrosion barrier to protect the sintered material 302 from corrosion and other interaction in chemical mechanical polishing applications.

FIG. 15A shows a slurry containing abrasive particles dispersed on master plate. The master plate may be coated with a non stick substance such as Teflon or other low energy surface material to prevent strong adhesion forces. The film thickness can be a monolayer of material applied or thicker. The description herein omits showing the low surface tension film on the master plate. The slurry is formed of a carrier fluid 404 and abrasive particles 402. The slurry is dispersed on the master plate 400 to provide a uniformly particle dispersion with a uniform particle distribution density on the master plate. FIG. 15B shows the carrier fluid evaporated from the master plate surface leaving abrasive particles distributed uniformly. The carrier fluid can be a low volatility fluid such as alcohol or water. FIG. 15C shows a process containing two steps. The first deposition step deposits a seed layer 412 to provide a conductive path required for an electro-deposition process. The seed layer can be sputtered or evaporated onto the master plate 400 containing the abrasive particles 402. An additional substrate layer formed from Cupper or Tin or Nickel 410 is then deposited on top of the conductive seed layer 412. The metal formed a matrix encapsulating the abrasive particles. The seed layer 412 can be few nanometers thick to provide a conductive path for the electro-deposition of the substrate layer. The seed layer is usually Chrome but other candidates are readily available. The substrate layer is deposited from an electro platting process for example. Cupper and Tin materials can be grown to many microns thick with very low film stress. A dry process such as MOCVD to deposit the substrate material is preferred as an initial deposition process to lock the abrasive particles in place. Once the abrasive particles are secured a wet process can be applied. Wet deposition processes such as electroplating are economical. Once the thickness of the substrate reaches a desired value, 20 microns for example, the substrate containing the abrasives is removed from the master plate as shown in FIG. 15D. Further etching on the surface containing the abrasive particles removes a substantially uniform thickness of the substrate layer exposes the abrasive particles 402 with a uniform height 420 as shown in FIG. 15E. The height of the protruding abrasive particles 420 matches the amount of material etched from the substrate surface.

FIG. 16A shows a slurry containing a carrier fluid 504 and abrasive particles 502 dispersed on a master plate 500. The slurry is dispersed on the master plate 500 to provide a uniformly dispersed particle distribution onto the master plate. The thickness of the fluid carrier 508 is controlled to match the desired abrasive protrusion. The fluid carrier is cross linked by thermal or irradiative processes such as UV process to form a cured polymer structure layer to accept a seed layer. FIG. 16B gives a depiction of a seed layer 510 deposited on the polymeric structure 512 and the abrasive particles 502. The seed layer 510 can be sputtered or evaporated onto the polymer structure 512 containing the abrasive particles 502. The seed layer can be Chrome or Nickel to promote the electroplating of an additional substrate layer formed from Cupper, Tin or Nickel. The seed layer can be few nanometers thick to provide a conductive path for the electro-deposition of the substrate layer. The substrate layer is deposited from an electro platting process for example. Cupper and Tin materials can be grown to many microns thick with very low residual film stress. Once the thickness of the substrate reaches a desired value, 20 microns for example, the substrate containing the polymer spacer and the abrasives is removed from the master plate as shown in FIG. 16C. Further etching on the surface containing the abrasive particles removes the soft polymer layer revealing the particle abrasives with a uniform height 520 matching the thickness of the polymeric film. The height of the particle abrasives matches the thickness of the polymeric spacer.

Where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit unless the context clearly dictates otherwise, between the upper and lower limit of that range and any other stated or intervening value in that stated range is encompassed within the inventions. The upper and lower limits of these smaller ranges which may independently be included in the smaller ranges is also encompassed within the inventions, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either both of those included limits are also included in the inventions.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which these inventions belong. Although any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present inventions, the preferred methods and materials are now described. All patents and publications mentioned herein, including those cited in the Background of the application, are hereby incorporated by reference to disclose and described the methods and/or materials in connection with which the publications are cited.

The publications discussed herein are provided solely for their disclosure prior to the filing date of the present application. Nothing herein is to be construed as an admission that the present inventions are not entitled to antedate such publication by virtue of prior invention. Further, the dates of publication provided may be different from the actual publication dates which may need to be independently confirmed.

Other embodiments of the invention are possible. Although the description above contains much specificity, these should not be construed as limiting the scope of the invention, but as merely providing illustrations of some of the presently preferred embodiments of this invention. It is also contemplated that various combinations or sub-combinations of the specific features and aspects of the embodiments may be made and still fall within the scope of the inventions. It should be understood that various features and aspects of the disclosed embodiments can be combined with or substituted for one another in order to form varying modes of the disclosed inventions. Thus, it is intended that the scope of at least some of the present inventions herein disclosed should not be limited by the particular disclosed embodiments described above.

Thus the scope of this invention should be determined by the appended claims and their legal equivalents. Therefore, it will be appreciated that the scope of the present invention fully encompasses other embodiments which may become obvious to those skilled in the art, and that the scope of the present invention is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more.” All structural, chemical, and functional equivalents to the elements of the above-described preferred embodiment that are known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the present claims. Moreover, it is not necessary for a device or method to address each and every problem sought to be solved by the present invention, for it to be encompassed by the present claims. Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims. 

1. A method of making an abrasive article comprising: preparing a master plate with a surface having a shape; depositing a spacer layer on the surface of the master plate; distributing a slurry containing an adhesive and abrasive particles on a surface of the spacer layer, wherein the abrasive particle comprise a primary diameter greater than a thickness of the spacer layer; pressing a substrate having a surface generally complementary to the surface of the master plate against the slurry with sufficient force to embed the abrasive particles into the substrate, and to penetrate the spacer and contact the reference plane defined by the master plate; at least partially curing the adhesive to form a reference surface between the abrasive particles with a shape generally complementary to the surface of the spacer layer; and separating the master plate and the spacer layer from the substrate to expose abrasive particle protruding a substantially uniform height above the reference surface formed by the cured adhesive.
 2. The method of claim 1 further comprising preparing the master plate and the substrate with one of flat, concave, convex, curvilinear, spherical, or grooved surfaces.
 3. The method of claim 1 wherein the step of depositing the spacer layer comprises one of spraying, coating, or printing the spacer layer on the surface of the master plate.
 4. The method of claim 1 further comprising applying a hard coat to the surface of the master plate before depositing the spacer layer.
 5. The method of claim 1 wherein the substrate is selected from one of metals, polymeric materials, ceramics, and composites thereof.
 6. A method of making an abrasive article comprising: preparing a master plate with a surface having a shape; depositing a spacer layer on the surface of the master plate; distributing a slurry containing abrasive particles on a surface of the spacer layer, wherein the abrasive particle comprise a primary diameter greater than a thickness of the spacer layer; pressing a substrate having a surface generally complementary to the surface of the master plate against the slurry with sufficient force to embed the abrasive particles into the substrate, and to penetrate the spacer and contact the reference plane defined by the master plate; separating the master plate and the spacer layer from the substrate to expose abrasive particle protruding a substantially uniform height above the reference surface formed by the master plate.
 7. The method of claim 6 further comprising applying a hard coat to the surface of the master plate before depositing the spacer layer.
 8. A method of making an abrasive article comprising: preparing a master plate with a surface having a shape; forming a surface barrier on the master plate; distributing a slurry containing a carrier fluid and abrasive particles on; evaporating carrier fluid from the slurry; depositing a substrate layer on to the seed layer containing a bottom surface charged with abrasive particles and a top surface containing the substrate material; releasing the substrate containing the abrasive particles from the master plate; and etching the bottom surface of the substrate layer to reveal the abrasive particles.
 9. The method of claim 8 further comprising depositing a seed layer onto the master plate containing the abrasive particles prior to the deposition of the substrate layer.
 10. The method of claim 8 further comprising preparing the master plate and the substrate with one of flat, concave, convex, curvilinear, spherical, or grooved surfaces.
 11. The method of claim 8 further comprising machining features into the surface of the master plate.
 12. The method of claim 8 wherein depositing the spacer layer comprises one of spraying, coating, or printing the spacer layer on the surface of the master plate.
 13. The method of claim 8 wherein the evaporating spacer layer is alcohol or water.
 14. The method of claim 8 wherein the substrate is metallic selected from low stress electrodeposited metals and its corresponding alloys.
 15. A substrate article of claim 8 further comprising a plurality of abrasive particles protruding a substantially uniform height above the etched surface.
 16. A method of making an abrasive article comprising: preparing a master plate with a surface having a shape; distributing a slurry containing an a carrier fluid and abrasive particles on a surface of the spacer layer; hardening the carrier fluid from the slurry; depositing a substrate layer on to the seed layer containing a bottom surface charged with abrasive particles and a top surface containing the substrate material; releasing the substrate containing the abrasive particles from the master plate; and etching the bottom surface of the substrate layer to reveal the abrasive particles.
 17. The method of claim 16 further comprising depositing a seed layer onto the master plate containing the abrasive particles prior to the deposition of the substrate layer.
 18. The method of claim 16 further comprising preparing the master plate and the substrate with one of flat, concave, convex, curvilinear, spherical, or grooved surfaces.
 19. The method of claim 16 further comprising the step of machining features into the surface of the master plate.
 20. The method of claim 16 wherein depositing the spacer layer comprises one of spraying, coating, dip coating, spin coating, or printing the spacer layer on the surface of the master plate.
 21. The method of claim 16 wherein the deposited material is Cupper, Nickel, Chrome, or Tin and their corresponding alloys.
 22. An abrasive article of claim 16 comprising a plurality of abrasive particles protruding a substantially uniform height above the deposited seed layer.
 23. A method of lapping a surface of a work piece comprising: positioning an abrasive article opposite the surface of the work piece; applying a lubricant to the abrasive article; and engaging the surface of the work piece with the abrasive particles and moving the work piece relative to the abrasive article to form a substantial bearing ratio between the surface of the work piece and the reference surface on the abrasive article.
 24. The method of claim 23 wherein the work piece comprises one of machined metal parts, silicon wafers, slider bars for hard disk drives. 